Eta Carinae (Eta Car) is located within the Carina nebula, approx 7,500 light years away. It is in fact a stellar system containing two stars, the larger with a mass off around 100 solar masses and the smaller star about 30 solar masses.

Eta Carinae brightened dramatically between 1835 to 1855 (which came to be known as 'The Great Eruption') where the larger star ejected about 30 solar masses worth of material and Eta Car brightened to be the second brightest 'star' in the night sky. It then faded over the next few decades only to have another minor eruption in the 1890s.  It then faded again but has since progressively brightened again through the 20th century.

During the Great Eruption, the material ejected from the star formed what is known as the Homunculus nebula consisting of two large polar bubbles and two smaller equatorial bubbles. The Homunculus nebula is gradually growing in size. 

My goal was to capture some degree of detail/shape of the Homunculus nebula which is a challenge because Eta Car is extremely bright even when using very short exposures.

So I decided to take 2min exposures for Ha, SII and OIII to capture the area of the Carina nebula around the Keyhole nebula (where Eta Car is located). 
Two minute exposures was more than enough as the Carina Nebula is quite a bright nebula in general.
A lot of interesting detail was seen in the SII filter so I tried to make them as prominent as possible without being overrun by the Ha and OIII.

For Eta Car, I decided on 0.2sec subs for R, G and B and 1 sec subs for Ha to produce an HaRGB image of the Homunculus nebula and it's immediate surrounding Ha emission nebula.


In this image of Eta Car, you can see the Ha region immediately surrounding the Homunculus and the arrows point to bulges of Hydrogen alpha emission energized by the UV equatorial emissions.




Blending the Homunculus nebula with the surrounding nebulosity of the Carina nebula, whilst trying to at least partially preserve the hydrogen emissions immediately surrounding the Homunculus, was quite a challenge.

Other notable areas in this region of the Carina Nebula include the Bok globule affectionately referred to as 'The Finger of God' or the 'Defiant Finger' and the so called 'Mystic Mountain' made famous in the Hubble image.